The present invention relates to a magnet target and a magnetron sputtering apparatus having the same.
During a process of magnetron sputtering, ionization degree of sputtering gas is relatively high to obtain a relatively high depositing rate of sputtering target, and in turn, to obtain a relatively high ionization degree of sputtering gas, a sufficiently large collision probability between electrons and sputtering gas molecules should be guaranteed. Accordingly, a magnet target is used in a magnetron sputtering apparatus to control electron trajectory in a helical form (as shown in FIG. 1).
When an electron travels in a magnetic field, the electron is subject to Lorentz force due to an angle between the velocity of the electron and the direction of the magnetic field and thus trends to conduct a circular motion. Furthermore, due to the presence of an electric field, the electron has acceleration in the direction opposite to that of the electric field. As a result, the electron moves forward helically under the action of both the magnetic field and the electric field. In this way, the motion path of the electron is elongated, and in turn the collision probability of the electron with the sputtering gas molecules is enhanced.
At present, most magnet targets adopt bar-like permanent magnets to provide a magnetic field for sputtering. As shown in FIGS. 2 and 3, a plurality of bar-like permanent magnets in a magnet target are fixed onto a fixing plate 3 side by side, including bar-like permanent magnets 1 having an internal N pole and an external S pole and bar-like permanent magnets 2 having an internal S pole and an external N pole. The bar-like permanent magnets 1 and 2 are arranged alternately. The magnetic field distribution characteristics of the bar-like permanent magnets fixed in the magnet target bring about a magnetic field having a non-uniform magnetic induction strength parallel to sputtering target in the magnetron sputtering region. Effects of Lorentz force on the electrons at different positions in the non-uniform magnetic field are different. If the magnetic induction strength is larger at a position, the cycle of the circular motion of an electron is smaller; as a result, a helical motion is more obvious and accordingly the probability that electrons and sputtering gas molecules collide with each other to ionize the sputtering gas molecules at the position is relatively larger. As shown in FIG. 4, the probability that sputtering target corresponding to a region where relatively larger magnetic induction strength presents is bombarded by the sputtering gas molecules is larger than the probability that the sputtering target in the remaining region is bombarded by sputtering gas molecules, which causes obvious local consumption of sputtering target and severe reduction of lifespan of sputtering target.
When a magnet moves at a uniform velocity, the magnetic induction strength generated per unit time in the region covered by the motion track of the magnet is substantively constant. Accordingly, based on this principle, there are proposed several approaches for improving uniformity of magnetic induction strength by moving magnet target to traverse the problem of obvious local consumption of sputtering target in a magnetron sputtering apparatus.
As shown in FIGS. 5 and 6, a plurality of bar-like permanent magnets 1 having internal N poles and external S poles and a plurality of bar-like permanent magnets 2 having internal S poles and external N poles are arranged alternately and fixed side by side onto two bar-like fixing plates 3 perpendicular to the permanent magnets 1 and 2. The fixing plates 3 reciprocate along the plane parallel to the sputtering target, so that the uniformity of the magnetic induction strength in the magnetron sputtering region can be improved. However, as during the motion of the magnet target, the speed of the magnet target varies; the maximum speed appears at the middle of the motion path and the minimum speed at edges. The uniformity of the magnetic induction strength in the central region of the sputtering target can be improved while the uniformity of the magnetic induction strength of the marginal portion of the sputtering target has a limited improvement only. Therefore, with this improving approach, the problem of obvious local consumption in the middle of a sputtering target can only be partially solved, while local consumption in the marginal portion of the sputtering target remains serious.
In addition to the above described approach, there is another approach for addressing the problem of obvious local consumption of sputtering target as follows.
As shown in FIGS. 7 and 8, a plurality of bar-like permanent magnets 1 having internal N poles and external S poles and a plurality of bar-like permanent magnets 2 having internal S poles and external N poles are arranged alternately and fixed side by side onto an endless belt 4 rotating at a constant speed and thus conduct a periodical motion parallel to a plane of sputtering target, so that a magnetic field of relatively uniform magnetic induction strength is generated in a magnetron sputtering region. This approach improves not only uniformity of magnetic induction strength in the central region of sputtering target but also uniformity of magnetic induction strength in marginal portion of the sputtering target. However, this approach improves mainly the uniformity in the movement direction of sputtering target, while uniformity of magnetic field in the direction perpendicular to the movement direction is almost not improved.